1. Field of the invention
The present invention relates to a waterproof camera usable both on land and under water.
2. Description of the prior art
Conventionally, there has been provided a number of waterproof cameras with waterproof casings to enable underwater photographing.
In the waterproof cameras according to the prior art, however, the lens mount of the camera body and the body mounts of the lens barrels in the plurality of interchangeable lenses are not waterproofed. Thus, in the case of the waterproof camera having such construction, it is impossible to change the interchangeable lens in the water for such purposes as the alteration of the angle of view of the photographing optical system, since such attempt will inevitably cause the water to enter inside the camera body and lens barrel.
As one of the solutions to this problem, there may be provided a method using the front converter to change the focal length which is to be attached in front of the photographing lens in order to change the angle of view of the photographing optical system. The above method, however, is disadvantageous in that the front converter deteriorates the aberrations of the photographing optical system in comparison with that of the photographing lens only. Another disadvantage of the method is that the camera cannot be used on land, since the waterproof camera using said front converter is operable on the condition that the space between said front converter and photographing lens is filled with the water.
Furthermore, in the method using interchangeable lenses and a front converter to change the angle of view to be photographed, such lenses and converter need to be carried separately from the camer, and this is especially disadvantageous for waterproof cameras, since the freedom in the movement of the user is restricted because of this.
As another solution to said problem, there may be provided a method that enables the change of the angle of view without using such things as interchangeable lenses and a front converter which are to be carried separately from the camera body, that is, a method using the zoom lens that enables the focal length to be varied or using the bifocal camera in which two different focal lengths of a photographing optical system can be selectively set. Such methods, however, when applied to the waterproof camera, increase the dimensions of the camera further because of the space required for the zooming mechanism and lens switching mechanism.
In addition the waterproof camera is generally larger than the ordinary camera because of its waterproof construction, and this is undesirable, since importance should be attached to the compactness in the case of the waterproof camera.